1. Field of the Invention
The present invention relates to a method of mounting a heat conductive member for an electronic component.
2. Description of the Prior Art
An LSI (Large-Scale Integrated circuit) chip is mounted on a small-sized substrate in an LSI package, for example. A stiffener surrounds the LSI chip on the surface of the substrate. The stiffener contributes to enhancement of the rigidity of the substrate. A heat conductive member or heat spreader is fixed to the surface of the LSI chip. The stiffener is interposed between the heat spreader and the substrate.
A solid solder material is first placed on the LSI chip in a method of making the LSI package. The heat spreader is superposed on the surface of the solid solder material. The stiffener is interposed between the heat spreader and the substrate. A thermosetting adhesive is interposed between the heat spreader and the stiffener as well as between the substrate and the stiffener. Heat is then applied to the solder material and the thermosetting adhesive. The solder material and the thermosetting adhesive melt and are hardened or cured. The heat spreader is in this manner fixed on the surface of the LSI chip. Simultaneously, the stiffener is fixed between the heat spreader and the substrate.
An oven is utilized to heat the LSI chip and the substrate. The temperature inside the oven is set higher than the melting point of the solder material and the curing temperature of the thermosetting adhesive. While the solder material melts on the LSI chip, the thermosetting adhesive melts on and below the stiffener. The heat spreader thus moves downward to get closer to the substrate. The thickness of the solder material in this manner depends on the weight and/or the urging force of the heat spreader. An excessive increase in the thickness of the solder material induces a deteriorated efficiency of heat transfer across the solder material. An excessive reduction in the thickness of solder material induces an unintentional detachment of the heat spreader from the LSI chip.